1. Chihara, Th. S.: An Introduction to Orthogonal Polynomials. New York-London-Paris: Gordon and Breach. 1978.
2. Cryer, C. W.: Rodrigues' formula and the classical orthogonal polynomials. Boll. Un. Mat. Ital.25, 1?11 (1970).
3. Dunkl, C. F.: A Krawtchouk polynomial addition theorem and wreath products of symmetric groups. Indiana Univ. Math. J.25, 335?358 (1976).
4. Fort, T.: Finite Differences and Difference Equations in the Real Domain. Oxford University Press. 1948.
5. Gröbner, W., Lesky, P.: Mathematische Methoden der Physik I. Mannheim: Bibl. Inst.89. 1964.